The purpose of the agricultural preserve program is to encourage property owners to continue the agricultural use of their land instead of converting it to nonagricultural uses. This is accomplished by giving property owners a reduction in the property taxes for their agricultural land in exchange for long term commitments to retain the land in agriculture. An agricultural preserve is established through a Land Conservation Contract signed by the owners of the property in agriculture and the County. This contract is founded upon the provisions of the California Government Code sections known as the California Land Conservation Act of 1965 or as the Williamson Act (Section 51200, et. seq.). The Williamson Act allows the County of Riverside to designate agricultural preserves wherein agricultural properties will be assessed on the basis of agricultural production rather than the current market value.

Establishing an agricultural preserve requires 100 contiguous acres under one or more ownerships. Landowners with less than 100 acres may apply for annexation to an existing agricultural preserve having a common boundary with their property. The minimum parcel size for annexation to a preserve is 10 acres.

The property to be included in an agricultural preserve must have agricultural zoning as defined in Ordinance 348, Section 21.3. An agricultural zone is classified as  A-1, A-2, A-P, A-D or C-V. If such zoning is not currently in place, the landowner must file a petition for a change of zone, with the appropriate fees, to amend the zoning to such an agricultural zone. A 10 or 20-acre minimum lot size will also be placed upon the agricultural zoning for an agricultural preserve.

All agricultural preserve applications may be filed only between March 1 and October 31 of any given year. Each application must be accompanied with the appropriate filing fee. After filing with the Riverside County Planning Department, the application will be reviewed by the Comprehensive Agricultural Preserve Technical Advisory Committee and then submitted to the Board of Supervisors for public hearing. The Board of Supervisors may approve, with changes, or deny the application.

In order to have land within an agricultural preserve assessed on the basis of agricultural production rather than full market value, the property owner and the County of Riverside must enter into a Land Conservation Contract. State law requires that a Land Conservation Contract is an enforceable restriction that must be administered by the County in a manner as to accomplish the purposes of the Williamson Act. The legislation has declared these purposes to include "...the preservation of a maximum amount of the limited supply of agricultural land..." and "...the discouragement of premature and unnecessary conversion of agricultural land to urban areas..." When an application is approved by the Board of Supervisors, and Land Conservation Contract is sent to each owner; these must be signed and notarized before final approval will be given. The owner has 90 days from the initial approval to return the signed contract. If he does not, the application to enter the Agricultural Preserve program will be nullified.

Land Conservation contracts executed under the regulations of the Williamson Act are in effect for ten years from the anniversary date of the contract. Contracts are automatically renewed for one additional year, on each anniversary date of the contract. Therefore, the contract will be in effect indefinitely. The automatic renewal of the contract can be terminated through the recording of a Notice of Nonrenewal on the contract. The provisions of the Contract restrict succeeding owners of the land, for the life of the contract.

After an agricultural preserve has been established, the land within the preserve is automatically restricted to the agricultural and compatible uses specified in Riverside County Ordinance No. 509.